Characterization of the vascular control of hindlimb metabolism

The constant-flow perfused rat hindlimb was used as a model to characterize norepinephrine (NE, noradrenaline)- and serotonin (5-HT)-mediated vasoconstriction and their associated effects on metabolism. Rat hindlimbs of various sizes were perfused using medium with or without erythrocytes at temperatures varying between 25 and 37°C. Varying these perfusion parameters altered the quantitative, but not qualitative, effects of the hormones. In the hindlimb, infusion of NE stimulated both a1- and b-adrenoceptors (AR). The overall effect was the rapid onset of a sustained increase in perfusion pressure which was only slightly increased upon b-AR blockade. Energy for NE-stimulated vasoconstriction was supplied via aerobic means, involving oxidative formation of ATP. In addition, vasoconstriction appeared to be dependent on extracellular Ca2+, suggesting an a1A-AR-stimulated Ca2+ influx through plasma membrane channels.